Anaerobic fermentation occurs during ruminant digestion, during which proteins and carbohydrates are degraded. It is desirable in ruminant digestion to be able to control protease and carbohydrase activity to optimize the digestive process.
Since feed is a major cost in ruminant production, enhancing digestive efficiency remains a driving objective in the industry. Although forages remain the major feed source, it is widely believed that the efficiency of feed utilization by ruminants has remained relatively unchanged during the last two decades. New innovations that enhance the digestive efficiency provide a compromise to emerging environmental concerns regarding ground water pollution in most dairying areas. Nevertheless, an in depth understanding of the roles of feed processing and bacterial digestion are required to fully manipulate the digestive processes of the rumen. Cheng et al. ("Microbial ecology and physiology of feed degradation within the rumen," in Physiological aspects of digestion and metabolism in ruminants: Proceedings of the seventh international symposium on ruminant physiology, Tsuda, Ed., 1991) has identified the following three general factors as influencing microbial digestion of feeds: (a) plant structures that regulate bacterial access to nutrients; (b) microbial factors that control adhesion and the development of digestive microbial consortia; and (c) complexes of oriented hydrolytic enzymes of the adherent microorganisms. Feed processing practices, e.g., grinding, normally attempt to increase enzyme-substrate interaction by the exposition of susceptible substrate binding sites.
The manipulation of digestion within the rumen in order to increase the efficiency of feed utilization has been achieved through the use of exogenous enzymes (Feng et al., "Effect of enzyme additives on in situ and in vitro degradation of mature cool-season grass forage," J. Anim. Sci. 70 (Suppl. 1):309 (1996)), and such compounds as ionophore antibiotics, methane production inhibitors, inhibitors of proteolysis or deamination, and buffers (Jouany, "Methods of manipulating the microbial metabolism in the rumen," Ann. Zootech. 43:49-62 (1994)). The increased digestive efficiency realized through the use of these compounds is the result of major shifts in microbial fermentation pathways. For example, the selective use of antibiotics can alter the rumen microbial population and ultimately influence the end products of digestion. Antibiotics are, however, used only in meat producing animals because of the risk of antibiotic transfer to milk. Production responses of animals fed exogenous enzymes have been inconsistent. Exogenous enzymes have been shown to increase (Beauchemin et al., "Fibrolytic enzymes increase fiber digestibility and growth rate of steers fed dry forages," Can. J. Anim. Sci. 75:641-644 (1995)), to not affect (Perry et al., "Effects of supplemental enzymes on nitrogen balance, digestibility of energy and nutrients and on growth and feed efficiency of cattle," J. Anim. Sci. 25:760-764 (1966)), and even to decrease (Svozil et al., "Application of a cellulolytic preparation in nutrition of lambs" Sbor. Ved. Praci. VUVZ Prhrelice 22:69-78 (1989)) the growth performance of ruminants fed forage or concentrate-based diets. The inconsistency is partly due to the numerous enzyme preparations available, application methods, and their interaction with different types of diets.
Long-chain fatty acids and the halogen homologues of methane have been found to reduce methane production in the rumen (Van Nevel et al., "Manipulation of rumen fermentation," In: The Rumen Microbial Ecosystem., Ed. P. N. Hobson. Elsevier Applied Science, London, pp. 387 et seq. (1988)). The reduction in methane production is usually associated with a decrease in deamination of amino acids, particularly, branched-chain amino acids and an increase in propionic acid production. The main limitation with the use of these additives is that rumen microbes are able to adapt and degrade them after about one month of treatment. Another disadvantage is that the beneficial effect appears to be consistent only in forage-based diets that favor methane production.
Buffers are mainly used under conditions where the feeding of high levels of grains can induce an active fermentation and cause excess production of acids within the rumen. They act by regulating and maintaining the pH at levels at which the cellulolytic microorganisms can be of maximum effectiveness (pH=6-7). The digestion of starch and proteins is generally decreased when buffers are fed, however, the effect on the digestion of cell wall carbohydrates is inconsistent (Jouany, "Methods of manipulating the microbial metabolism in the rumen," Ann. Zootech. 43:49-62 (1994)).
Surfactants have been used in the food processing industry as emulsifiers and extenders (Griffin et al., "Surface Active Agents," in Handbook of Food Additives.2.sup.nd Ed., T. E. Furia, Ed., CRC Press, New York, N.Y., p 397 et seq. (1972)) and also as cleaning agents. The most well known physicochemical property of surfactants is their interfacial activity when placed in solution. Their ability to align at the interfaces is a reflection of their tendency to assume the most energetically stable orientation. One type of nonionic surfactant, the polyoxyethylene sorbitan esters, are synthesized by the addition, via polymerization, of ethylene oxide to sorbitan fatty acid esters. These nonionic hydrophilic emulsifiers are very effective antistaling agents and are therefore used in a variety of bakery products. They are widely known as polysorbates. The effects of the polysorbate Tween 80 on the hydrolysis of newspaper was investigated by Castanon et al., "Effects of the surfactant Tween 80 on enzymatic hydrolysis of newspaper," Biotechnol. & Bioeng. 23:1365 (1981). However, the effects of nonionic surfactants on ruminant digestion have not heretofore been contemplated.
The present invention provides compositions and methods that utilize nonionic surfactants to optimize the digestive process in ruminant animals. The compositions and methods described in this invention enhance productivity of ruminant animals, reduce waste production and ultimately improve profitability.